Installation Guide

507052-04 Page 23 of 53Issue 1727
Table 8.
Maximum Allowable Exhaust Vent Pipe Length (in ft.) without Insulation in Unconditioned Space for Winter Design
Temperatures
Winter Design Temperatures
1
ºF
(ºC)
Vent Pipe
Diameter
Unit Input Size
045 070 090 110
32 to 21
(0 to -6)
PVC
2
PP PVC
2
PP PVC
2
PP PVC
2
PP
2 in. 21 18 33 30 46 42 30 30
2-1/2 in. 16 N/A 26 N/A 37 N/A 36 N/A
3 in. 12 12 21 21 30 30 29 29
20 to 1
(-7 to -17)
2 in. 11 9 19 17 28 25 27 24
2-1/2 in. 7 N/A 14 N/A 21 N/A 20 N/A
3 in. N/A N/A 9 9 16 16 14 14
0 to -20
(-18 to -29)
2 in. 6 4 12 10 19 16 18 15
2-1/2 in. N/A N/A 7 N/A 13 N/A 12 N/A
3 in. N/A N/A N/A N/A 8 8 7 7
1
Refer to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook.
2
Poly-Propylene vent pipe (PP) by Duravent and Centrotherm
NOTE - Concentric terminations are the equivalent of 5’ and should be considered when measuring pipe length.
NOTE- Maximum uninsulated vent lengths listed may include the termination (vent pipe exterior to the structure ) and cannot exceed
5 linear feet or the maximum allowable intake or exhaust vent length listed in Table 6 or Table 7A through Table 7C.
NOTE - If insulation is required an unconditioned space, it must be located on the pipe closed to the furnace.
Conditioned
Space
Unconditioned
Space
Exhaust
Pipe
Intake
Pipe
Conditioned
Space
Pipe Insulation
Figure 27. Insulating Exhaust Pipe in an Unconditioned Space